1. Field of Invention
The present invention relates to a pneumatic tire having a tread pattern.
2. Background Information
Conventionally, in order to obtain an efficient drainage of water which entered between a tread pattern and the ground, a contact patch of a continuously extending land portion sandwiched between two tire circumferential main grooves and extending in a tire circumferential direction is formed in bulging shapes at a front portion of a leading edge and at a rear portion of a trailing edge in a pneumatic tire. In this way, the water which collided with the continuously extending land portion is divided into the tire circumferential main grooves located on opposite sides and efficiently drains rearward from the trailing edge.
In the above method, however, it is impossible to form the contact patch shape of the continuously extending land portion into an excessively bulging shape in the tire contact patch shape of the tire, because it reduces a contact area in contact with the ground. Reduction of the contact area causes less quality of handling and stability performance. Under this circumstance, there is a known pneumatic tire in which handling and stability and hydroplaning resistance (hydroplaning preventing performance) are compatible with each other at high level as described in Japanese Patent No. 4453435.
To put it concretely, the pneumatic tire is a pneumatic tire in which a pair of main grooves continuously extending in a tire circumferential direction on opposite sides of a tire equator (tire center line) is provided in a tread portion and a center rib continuous in the tire circumferential direction is formed between these main grooves. In this pneumatic tire, a sectional profile line of a tread of the center rib intersects with a virtual tread profile line smoothly connecting a tread surface including opposite contact patch side edges and excluding the center rib, and a central portion in a tire axial direction of the center rib is formed into a smoothly bulging shape toward an outer side of a tire radial direction and swells from the virtual tread profile line to the outer side of the tire radial direction. A swelling amount A of the center rib from the virtual tread profile line is 0.5 mm to 3.0 mm, while ridge lines are formed by the tread face and side walls of the center rib, and the ridges sink at opposite edge portions of the center rib into an inner side of the virtual tread profile line in the tire radial direction.